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Experiment of thermal cracking and crack initiation mechanism of oil shale |
MENG Qiao rong, KANG Zhi qin, ZHAO Yang sheng, YANG Dong
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(Mining Technology Institute of Taiyuan University of Technology,Taiyuan 030024, China)
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Abstract: |
A 3D undamaged experiment of oil shale was carried out on the μCT225kVFCB micro focus CT machine, and the process of fissures appearance and development under different temperatures was observed. Based on the thermal elasticity and experimental results, the crack initiation mechanism of oil shale was analyzed. The results show that at 300 ℃, oil shale cracking is aroused from thermal stress which produced some fissures parallel to the surface of original bedding on cementation surface, and the crack initiation mechanism is that thermal stress exceeds the limit of rock strength. With the temperature exceeding 300 ℃, in the effect of the thermal stress and chemical reaction of the oil shale, all kinds of fissures grow widely, and the crack initiation mechanism is that the expansion pressure from chemolysis of source material exceeds critical expansion pressure of rock. As a result of these two crack initiation mechanisms, the connected fissures network is formed at 600 ℃ and oil and gas could seep out of oil shale, which makes in situ mining oil shale practicable. |
Key words: oil shale thermal cracking fissure crack initiation mechanism temperature |
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